Maybe you can put her mind at easy by going somewhere public. Don't leave your drink unattended and just feel him out and maybe have your mom come pick you up after? I can get feeling lonely and I'm glad he's making you happy. I do wish you the best but maybe it's better just simply going out to eat and hanging out instead.

Also maybe your mom can do a background check. She might just be worried but I know it's annoying.

You should do what you wish at the end of day I assume you're an adult but it is wise just to have a few hang out with him at first, but maybe not to go anywhere private.

I mean this in the kindest of possible ways, but your mom sounds batshit. Not even saying she doesn't have a foot to stand on.
Yes, this dude could be crazy, but you've been talking for a month. Hopefully you're looking for red flags (does he respect boundaries, etc). But otherwise, meeting in person after talking for 1-2 months daily isn't that crazy. And doing it in public is the safest choice.
Tell someone where you're going, when you plan to return/contact them, and who you're going with (all the info about the dude you can come up with). That's about as safe as you can get meeting randos. I see nothing wrong with that. If you don't check in on time, they know where you were last seen and who you're with. They can call the cops and hopefully you've provided enough info to be found quickly.
Then when you go to meet, just stay in public no matter what he wants. Stay in view of others.

Ok. You go on your date. Give me mind contacts, I'll keep her busy... 😌

Just play it smart
You’ll be fine
She’s being very very overprotective

Personally I wouldn't be telling my mum the details if she's going to freak out. You're smart enough to know how to keep yourself safe if you're meeting someone who you don't know well. Stuff like staying in a public well lit area, tell another friend you're meeting him and have her call you at a specific time to check you're ok and don't go anywhere alone until you have a good feel for what he's like. Trust your instincts.

Go with your gut feeling. Don't worry about your mom's opinions. You have to live your life for you. Remember that.

if your 14 years old. she may have a reason,

You COULD either take him to her house when she's there or have her chaperone the first meeting.
Just to ease her mind.

*RAPIST and *MURDERER.

Woah. I don't know you, or if you're being honest but, if so, I'm not sure your Mom is looking out for you. I think she's looking out for herself.

Your mother doesn’t want to lose you and will try to manipulate you to not be around anyone else but her.